1. Field of the Invention
The present invention relates to mycology, entomology and the use of fungal mycelium as insect attractants (mycoattractants) and biopesticides (mycopesticides). More particularly, the invention relates to the control and destruction of insects, including termites, fire ants, carpenter ants, flies, beetles, cockroaches, grasshoppers and other pests, using pre-sporulation fungal mycelium as an attractant and/or infectious agent.
2. Description of the Related Art
Insects are among the most diverse and numerous life forms on earth. While the majority of the one million named species of insects are considered beneficial, somewhere from 1% to 5% are considered to be pests. These insect pests cause tremendous losses in terms of direct destruction of crops, livestock and human dwellings and vector pathogens including protozoans, bacteria, viruses and rickettsia that cause devastating human health problems. The physical, mental, economic, social, and ecological implications of these pest insects are immeasurable on any scale.
The use of chemical pesticides is the cause of many secondary environmental problems aside from the death of the targeted pest. Numerous problems attributed to chemical pesticides are caused or compounded by widespread application necessitated by lack of suitable means of attracting the targeted pest to the pesticide. Communities are increasingly in need of natural solutions to pest problems.
Compounding these problems, many pest type or vermin insects have developed a broad spectrum of resistance to chemical pesticides, resulting in few commercially available pesticides that are effective without thorough and repeated applications. In addition to being largely ineffective and difficult and costly to apply as presently utilized, chemical pesticides present the further disadvantage of detrimental effects on non-target species, resulting in secondary pest outbreaks. Widespread use of broad-spectrum insecticides may destroy or greatly hamper the natural enemies of pest species, with pest species reinfesting the area faster than non-target species, thereby allowing and encouraging further pest outbreaks. Van Driesche, R. G. and T. S. Bellows Jr., Biological Control, Chapman & Hall, pp. 4-6 (1996). Further exacerbating these problems, introduced “alien” insect pests such as termites or fire ants often have few or no natural enemies. There is a particular need for natural alternatives.
Biological control agents have been tried with varying results. Bacteria such as Bacillus thuringiensis are used with some success as a spray on plants susceptible to infestation with certain insects. Fungal control agents are another promising group of insect pathogens suitable for use as biopesticides. However, limited availability, lack of effective delivery systems, reliability and cost has hampered the development of such fungal control agents. Host range and specificity has been a problem as well as an advantage: a fungal pathogen that is pathogenic (capable of causing disease) and virulent (in the sense of being extremely infectious, malignant or poisonous) to one insect species may be ineffective against other species, even closely related species of the same family or genus. However, some success has been demonstrated.
The typical lifecycle of the entomopathogenic (capable of causing insect disease) fungi is thought to involve adhesion of the spore(s) to the host insect cuticle, spore germination, penetration of the cuticle prior to growth in the hemocoel, death, saprophytic feeding, hyphal reemergence and sporulation. For example, U.S. Pat. No. 6,254,864 (2001) to Stimac et al. discloses dry powder Beauveria bassiana spore and spore/mycelium compositions for control of cockroaches and ants including carpenter ants, pharaoh ants and fire ants. U.S. Pat. No. 4,925,663 (1990) to Stimac discloses Beauveria bassiana used to control fire ants (Solenopsis). Rice, mycelia and spores (conidia) mixture may be applied to fire ants or used as a bait and carried down into the nest, thereby introducing spores. U.S. Pat. No. 5,683,689 (1997) to Stimac et al. discloses conidial control of cockroaches, carpenter ants, and pharaoh ants using strains of Beauveria bassiana grown on rice. U.S. Pat. No. 5,413,784 (1995) to Wright et al. discloses compositions and processes directed to the use of Beauveria bassiana and Paecilomyces fumosoroseus to control boll weevils, sweet potato whiteflies and cotton fleahoppers. U.S. Pat. No. 5,728,573 (1998) to Sugiura et al. discloses germinated fungi and rested spore termiticides of entomogenous fungus such as Beauveria brongniartii, Beauveria bassiana, Beauveria amorpha, Metarhizium anisopliae and Verticillium lecanii for use against insects such as termites, cockroaches, ants, pill wood lice, sow bugs, large centipedes, and shield centipedes. U.S. Pat. No. 5,939,065 (1999) and U.S. Pat. No. 6,261,553 (2001) to Bradley et al. discloses conidial formulations of Beauveria and methods for control of insects in the grasshopper family. U.S. Pat. No. 4,942,030 (1990) to Osborne discloses control of whiteflies and other pests with Paecilomyces fumosoroseus Apopka spore conidia formulations. The Paecilomyces fungus is also useful for control of Diptera, Hymenoptera, Lepidoptera, Bemisia, Dialeurodes, Thrips, Spodoptera (beet army worm), Leptinotarsa (Colorado potato beetle), Lymantria (Gypsy moth), Tetranychus, Frankliniella, Echinothrips, Planococcus (citrus mealybug) and Phenaococcus (solanum mealybug). U.S. Pat. No. 5,360,607 to Eyal et al. discloses prilled Paecilomyces fumosoroseus compositions utilizing mycelium grown via submerged fermentation to produce conidia to control various insects including whiteflies, mosquitoes, aphids, planthoppers, spittlebugs, mites, scales, thrips, beetles or caterpillars. U.S. Pat. No. 5,165,929 (1992) to Howell discloses use of Rhizopus nigricans and other fungus in the order Mucorales as a fungal ant killer. U.S. Pat. No. 5,989,898 (1999) to Jin et al. is directed to packaged fungal conidia, particularly Metarhizium and Beauveria. The scientific journal literature also discusses similar uses of conidial preparations.
One disadvantage to such approaches is that the fungal lifecycle may be particularly sensitive to and dependent upon conditions of humidity, moisture and free water, particularly during the stages of spore germination and sporulation after death of the insect.
A particular disadvantage with conidial preparations becomes apparent from U.S. Pat. No. 5,595,746 (1997) to Milner et al. for termite control, which discloses Metarhizium anisopliae conidia utilized as a termite repellant in uninfested areas and as a termite control method in infested areas. The difficulties of utilizing conidia or conidia/mycelium as a bait and/or contact insecticide are readily apparent when considering that conidia are effective as an insect repellant to termites and are repellant in varying degrees to most or all targeted insect pests. A repellant, of course, does not facilitate use as a bait or contact insecticide. This may be a factor in explaining why fungal insecticides have all too often proven more effective in the laboratory, where conidia may be unavoidable in the testing chamber or even directly applied to insects, than in the field.
U.S. Pat. No. 5,888,989 (1999) to Kern discloses synergistic combinations of conidia of entomopathogenic fungi such as Beauveria and Metarhizium with parapyrethroid insect compositions such as silafluofen and etofenprox, nitromethylenes such as imidacloprid, carbamates such as fenoxycarb and phenylpyrazoles such as fipronil. Problems remain with the repellency of the spores, the repellency of the pesticides and the use of conidia as a vector of infection.
Certain sexually reproducing brown-rot fungi (such as Lenzites trabea), dry rot fungi and other fungi are known to influence termite behaviors in laboratory and field tests, demonstrating attractant properties, eliciting trail-following, etc. See, for example, U.S. Pat. No. 4,363,798 (1982) to D'Orazio for termite baits utilizing brown rot fungus as an attractant mixed with toxicant boron compounds. The brown-rot fungus Lentinus lepideus and aqueous extracts of this fungus were found to be extremely lethal to termites in the laboratory, U.S. Pat. No. 3,249,492 (1966) to Lund. Certain fungi are known to produce substances that elicit trail-following in Rhinotermitidae in the laboratory, i.e., Gloephyllum trabeum, Oligoporous balsameus and Serpula lacrimans. Various extracts of the sexually reproducing Zygomycetes fungus Micromucor ramannianus and other fungi coexisting with Reticulitermes have also been shown to exhibit phagostimulatory (feeding stimulatory) effects and phagodeterrent effects. See U.S. Pat. No. 6,203,811 (2001) to McPherson et al. However, there remains a need for improved fungal attractants and pesticides.
The fresh, dried and rehydrated mycelium of entomopathogenic fungi has been utilized as a spore source in both the laboratory and field. See, for example, the U.S. patents above, where conidia are directly or indirectly produced from solid substrate or liquid fermentor grown mycelium. Pre-sporulation mycelium of Metarhizium anisopliae, Metarhizium flaviride, Beauveria bassiana, Paecilomyces farinosus, Paecilomyces lilacinus and Hirsutella citriformis has also been utilized as a spore source in agricultural fields for use against various subterranean and agricultural pests including the black vine weevil, the cranberry girdler (Chrysoteuchia topiaria), sod webworm, rice brown planthopper, stem borer, European corn borer and fall armyworm. See Booth and Shanks Jr., Potential of a Dried Rice/Mycelium Formulation of Entomopathogenic Fungi to Suppress Subterranean Pests in Small Fruits, Biocontrol Science and Technology, 8: pp. 197-206 (1998); Rombach et al., Infection of Rice Brown Planthopper, Nilaparvata lugens (Homoptera: Delphacidae), by Field Application of Entomopathogenic Hyphomycetes (Deuteromycotina), Environmental Entomology, 15(5): pp. 999-1110 (1986); and Maniania, Evaluation of three formulations of Beauveria bassiana (Bals.) Vuill. for control of the stem borer Chilo partellus (Swinhoe) (Lep., Pyralidae), Journal of Applied Entomology, 115: pp. 266-272 (1993). Pre-sporulation vegetative mycelium has also been a focus with the Entomophthorales mycopesticidal fungi such as Zoophthora radicans, which produce fragile, thin-walled spores that are difficult to mass produce, harvest and formulate on an industrial scale, thus leading to investigations of the also somewhat delicate and ephemeral mycelium. After being applied to the crop or soil, the mycelium produces spores that infect the target pests. See, for example, U.S. Pat. No. 4,530,834 (1985) to McCabe et al. Pre-sporulation mycelium of Hirsutella citriformis has been also been utilized in the field as conidia of the fungi are difficult to produce due to low sporulation rates, slime production of the mycelium and irregular growth patterns.
Another continuing problem with existing techniques for combating pests including social insects has been inconsistent bait acceptance. Baits are often bypassed and left uneaten by social insects such as termites and carpenter ants, which are hard to attract. Such may be a particular problem with insects such as termites and carpenter ants, as opposed to house ants and cockroaches, because it is usually not possible to remove competing food sources for termites and carpenter ants. Attractants, pheromones and feeding stimulants have sometimes increased the consistency of bait acceptance, but such increases cost and complexity, and there remains a continuing need for improved baits with improved bait acceptance.
There is, therefore, a continuing need for improved attractants and baits in general. There is a continuing need for enhancing the effectiveness of entomopathogenic fungal biopesticide products and methods and enhancing the attractiveness of such fungal pesticides to insects. There is also a need for improved packaging, shipping and delivery methods.
In view of the foregoing disadvantages inherent in the known types of insect control agents, the present invention provides improved fungal biocontrol agents and methods of using such agents.